The present invention relates generally to distributed numerical control systems and associated methods and, particularly, to systems and methods for transferring a numerical control program to thereby control a machine tool controller.
In many manufacturing processes today, computer-aided manufacturing (CAM) systems allow machine tools to manufacture parts without a lot of manual interaction. Generally, in CAM systems, once the planning and arrangement of machine tools for a particular manufacturing process have been set up, machining the parts can proceed automatically, often untouched by human hands. One part of most CAM systems is a process called numerical control (NC), in which instructions are coded into computer programs, called NC programs, that the machine tools use to guide them in the machining sequence.
Generally, a CAM system 10 is a closed-loop system that consist of NC programs, machine tool controllers 20 and the machine tools 30, as illustrated in FIG. 1. The machine tool controllers input the NC programs and decode the coded data into a format to thereby control the machine tools in the machining processes. Feedback loops from the machine tools to the machine tool controllers permit errors in the operations of the machine tools to be sensed by the machine tool controllers such that the machine tool controllers can adjust the operations of the machine tools to correct the errors.
In many complex manufacturing companies, multiple machine tool controllers within a machine shop are connected to a central mainframe database 40 over dedicated communication systems, such as serial communication, block transfer read communication or local area network (LAN) communication, to form a direct numerical control (DNC) system. In conventional DNC systems, the NC programs are housed within the mainframe database and are transferred to the various machine tool controllers, as desired. In this regard, proprietary computer software systems, such as TrueDNC distributed by Thedra Technologies, Inc. of Troy, Mich., can be operated from the mainframe database to transfer the NC programs to the connected machine tool controllers. Additionally, DNC systems can be used to transfer NC programs from machine tool controllers back to the central mainframe database, such as when a NC program has been edited at the machine tool controller.
While conventional DNC systems are adequate to control machine tool controllers within a single shop, they have several drawbacks. First, because the machine tool controllers of conventional DNC systems are connected to the mainframe database over dedicated communication systems, the distance over which the mainframe database can transfer the NC programs is typically limited. As manufacturing companies become more complex, many operate several shops often separated by great distances. For example, one manufacturing company could have one shop in California and a second shop in Pennsylvania. In such an instance, a NC program on a mainframe database in one shop could not be transferred to a machine tool controller in the second shop. Instead, a duplicate of the NC program would have to be maintained on a mainframe database in the second shop.
Second, conventional DNC systems typically require expensive proprietary computer software systems to transfer the NC programs back and forth between the mainframe database and the machine tool controllers. These computer software systems can generally only operate on a single mainframe database, typically requiring separate software licenses to operate on multiple mainframe databases located at different shops throughout a manufacturing company. Additionally, these computer software systems can typically only operate according to a format specific compatible with the machine tool controller controlled, requiring a reformatted software system, or a different software system, to operate machine tool controllers compatible with different formats.
In light of the foregoing background, the present invention provides an improved DNC system, method and computer-program product that utilize a wide area network (WAN), such as the Internet, to transfer NC programs to thereby control machine tool controllers. The DNC system of the present invention allows a user to select, from one location, NC programs from mainframe databases located at another location and thereafter transfer the selected NC programs to machine tool controllers located at a third location. Using the WAN to transfer the NC programs, the DNC system of the present invention overcomes the limited transfer range of conventional DNC systems.
In one embodiment, the DNC system of the present invention consists of at least one central processing element, such as a universal mainframe database, that includes the NC programs. By controlling machine tool controllers over the WAN, the DNC system of the present invention can control machine tool controllers located in different shops using one mainframe database, if so desired, in contrast to a mainframe database for each shop as required by conventional DNC systems. The system also includes a workstation connected to the central processing elements via the WAN. Additionally, the system includes at least one machine tool controller for receiving the selected NC programs across the WAN from the central processing elements. Based upon the selected NC programs, the machine tool controllers can control at least one machine tool during a manufacturing process.
In another embodiment, the system further includes at least one server processing element, such as a mainframe database local to specific shops. In this regard, the system allows the NC programs to be first transferred from the central processing elements to a shop local to the desired machine tool controllers before transferring the NC programs to the machine tool controllers, such as to account for scheduled maintenance shutdown periods of the central processing elements. The server processing elements are connected to the central processing elements via the WAN so that the central processing elements are capable of transferring the selected NC programs to the server processing elements. The server processing elements, in turn, are connected to the machine tool controllers so that the server processing elements are capable of transferring the selected NC programs to the machine tool controllers.
In a further embodiment, each central processing element includes a database that stores the NC programs and that operates according to a predetermined platform. In this embodiment, the workstation is capable of communicating with the database of each respective central processing element according to the respective platform in order to transfer the at least one NC program. In this regard, the system of the present invention is platform independent, such that the workstation can select and communicate with different mainframe databases that may each operate according to different platforms.
In operation, the NC programs are transferred via the WAN by first selecting the NC programs from the workstation. Then, via the WAN, the workstation notifies at least one of the central processing elements of the selected NC programs so the central processing elements can transfer the NC programs. In embodiments where the central processing elements each include a database operating according to a predetermined platform, the workstation communicates with the database of each respective central processing element according to the platform in order to notify the respective central processing element to of the selected NC programs to transfer. The notified central processing elements then transfer the selected NC programs across the WAN from the NC programs"" respective central processing elements to at least one machine tool controller. In a further embodiment, the NC programs are transferred to the machine tool controllers according to a predetermined protocol, such as a file transfer protocol (FTP). In embodiments including the server processing elements, the selected NC programs can first be transferred from the central processing elements across the WAN to their respective server processing elements. After the server processing elements have received the NC programs, either immediately or after a time period, the server processing elements can transfer the NC programs to their respective machine tool controller.
The machine tool controllers then use the NC programs to control respective machine tools. In one embodiment, each machine tool controller is capable of executing, or decoding, the NC programs according to a predetermined format, such as ASCII. In this embodiment, the selected NC programs are transferred to the machine tool controllers according to the format of each respective machine tool controller. In this regard, the system of the present invention is format independent in that it can transfer NC programs to machine tool controllers executing NC programs according to different formats.
Advantageously, because the workstation can select and transfer NC programs from a workstation located separately from both the mainframe databases and the machine tool controllers, such as between two shops separated by a great distance, the system of the present invention can also be used in conjunction with an enterprise resource planner (ERP) system. In this regard, the present invention provides a method and computer-program product that allows a user to control a plurality machine tool controllers with the NC programs according to a status of each machine tool controller. According to one embodiment, the method for controlling the machine tool controllers begins by selecting at least one machine tool controller from the plurality of machine tool controllers based upon a status of each machine tool. The status of each machine tool controller can be based upon any of a number of different factors, such as an operability status, a current workload status and a future workload status. Using the status of each machine tool controller, a user at the workstation can balance the workloads of the machine tool controllers or select operating machine tool controllers, for example. Then, after the machine tool controllers are selected, the NC programs are selected from the workstation, such as via the WAN. Next, the selected NC programs are transferred from the central processing elements to the selected machine tool controllers to thereby control the selected machine tool controllers.
Therefore, the present invention provides a system, an associated method and a computer-program product that utilize a WAN, such as the Internet, to transfer NC programs to thereby control machine tool controllers. The present invention overcomes the limited transfer range of conventional DNC systems by allowing users to select, from one location, NC programs from mainframe databases located at another location and thereafter transfer the selected NC programs to machine tool controllers located at a third location. The present invention can also operate platform and format independent by providing a workstation and central processing elements that can select, communicate and transfer NC programs depending on the platform and format of the central processing elements and machine tool controllers, respectively. In addition to an improved DNC system, the present invention also provides a new ability for a manufacturing planner, using an ERP system to push NC programs to machine tool controllers. In this regard, the present invention provides a method and computer-program product that allows a user to control a plurality machine tool controllers with the NC programs according to the status of each machine.